High altitude ice crystals that are not visible to the crew of an aircraft, especially at night, may present a hazard to the aircraft passing through an airspace region having high concentrations of the ice crystals. Such ice crystals, which may be encountered while flying through clouds, may cause power loss in a jet engine or even engine damage. Power loss may include engine instability, power surge, power rollback, stalling, and/or flameout.
These non-visible ice crystals may be found at altitudes between 9,000 and 40,000 feet, when the ambient temperature is between −5° C. to −55° C. High altitude ice crystals are typically associated with convective cloud formations, such as isolated cumulonimbus cloud formations, thunderstorms, or even tropical squall lines. Such convective cloud formations can contain areas of strong updrafts. The strong updrafts in the convective weather can lift liquid water thousands of feet into the atmosphere, and thus form ice crystals.
Regions of airspace having non-visible ice crystals may be at altitudes that are significantly higher than the visible tops of the convective cloud formations which formed the ice crystals. Further, high altitude winds may blow the ice crystals away from the convective cloud formations. Accordingly, regions of airspace having large concentrations of ice crystals may be encountered far above and/or away from the vicinity of the convective cloud formations which formed the ice crystals. Further, such airspace regions may have little to no turbulence to provide a warning indication to the crew of an aircraft as it flies into an airspace region with high concentrations of ice crystals.
Because of the very small size of the ice crystals, which may be as small as 40 microns, the ice crystals are not visibly detectable by the aircraft crew. Thus, the crew may not be aware that their aircraft is travelling through an airspace region having a high concentration of ice crystals, particularly if there is no turbulence and/or if the airspace region is not near any convective cloud formations.
Further, conventional aircraft weather radar systems are typically not configured to detect ice crystals since the reflectivity levels of return echoes from the ice crystals and/or the associated cloud cover, which may be in the range of 0-20 decibels (dBZ), is below the radar return sensitivity threshold levels, typically set at or about 20 dBZ. The aircraft weather radar systems are configured to detect larger water particles, such as rain, hail, and/or snow since these larger water particles provide radar reflectivity signal strength return levels that are discernable by the aircraft weather radar systems since such radar reflectivity signal strength return levels exceed the minimum radar return sensitivity threshold levels of approximately 20 dBZ. Low level radar reflectivity signal strength return levels that are less than a radar return sensitivity threshold level are typically ignored to reduce the amount of information presented on the radar system display. That is, since low levels of precipitation are typically not dangerous to aircraft, and since regions with low levels of precipitation exhibit low radar reflectivity signal strength return levels below the 20 dBZ threshold, such regions of low levels of precipitation are typically not indicated on the radar system display to avoid distracting the aircraft crew. Accordingly, the presence of ice crystals are not indicated on the radar system display because of their low radar reflectivity signal strength return levels.
Accordingly, there is a need in the arts to provide the crew of an aircraft information indicating the location of regions of airspace that are likely to have ice crystals so that the crew may then avoid airspace having potentially high concentrations of ice crystals.